I've used a couple hundred rounds of their 142gr SMK in 6.5CM. Accuracy and SD in my Tikka T3X TAC A1 is comparable to Hornady or Federal 140gr match rounds - e.g., pretty much everything shoots into 0.4 - 0.5 MOA @100 (5-round groups) when I do my part. The first hundred rounds were kinda slow - 2550fps measured by LabRadar chrono. Second hundred, a much more recent lot, averaged 2603. By comparison, the last lot of Hornady 140gr ELD Match ran 2656fps (early 2017-vintage lot).
I haven't shot much of their .223 out of my Wilde-chambered 1:8" twist AR. The rifle likes 75gr Hornady Steel Match as well as anything else I've tried through it; the Defender 69gr SMK ran 2625fps (18" barrel) and was similar in accuracy and SD.
Defender is based 90 minutes down the road from me; I've visited their showroom and see them at local shows. Good people.